You don't enter it anywhere. TurboTax will give it to you automatically based on the date of birth that you entered in your personal information.
The $6,000 senior deduction will be calculated* on 1040 Schedule 1-A page 2 Part V Enhanced Deduction for Seniors. From there, it goes to line 13b of form 1040. It is separate and in addition to the Standard Deduction or your Itemized Deductions on 1040 line 12e. Turbo Tax automatically includes it.
*Most people get the full $6000 ($12,000 married filing jointly). But for people over a certain income, it is reduced.
